Homosexual behavior in sheep
Homosexual behavior in sheep is common and well documented in domestic sheep (Ovis aries) and at least four species of wild sheep (members of the genus Ovis). About 8% to 10% of domestic rams (male sheep) refuse to mate with ewes (female sheep) but do readily mate with other rams, making them the only known mammal besides humans to exhibit exclusively same-sex sexual behavior.
Source: Wikipedia — Homosexual behavior in sheep (CC BY-SA 4.0)